Adequate Compression - CL72

Spike · Post by **Spike** » Wed Jun 01, 2011 10:28 pm

This a very original and unmolested 64 CL72 with 19,000 miles on the clock. It sat for about 30 years. Engine was frozen. With out teardown, I got it running about four months ago. It sat again and now it will not start. Back to basics. First compression.

What is the minimum compression needed for these bikes to start?

This one shows the following:

Leak down test at 60 psi input, loss is 6% left side, and about 20% right side. Cold, no oil added. This could stand a recheck as it is hard to get every thing set to hold pressure on the piston and crank. Pointers on proper technique to get a good leak down test are welcome.

Pump up test on a Harbor Freight tester results are three kicks to get about 90 psi on both sides, cold.

With oil added, still cold, three kicks gets about 100 psi.

Five kicks cold, no oil will build to 105 on the left and 115 on the right.

Five kicks after oil added, gets 155psi on left and 145 psi on right.

This does not seem stellar to me. The rings may be a little worn, but the motor should run on this shouldn't it? leaking is not through the exhaust, and does not seem to be from the intake. Carbs and air cleaners are installed so intake leakage would be hard to ascertain, right now.

Spike
Portland, OR

Airmun · Post by **Airmun** » Thu Jun 02, 2011 3:28 am

If it ran a couple of months ago, it should run now. Apply the old adage of compression, spark ,fuel.
I feel that the compression is more than adequate and would be looking at the other items. Good Luck.

Spike · Post by **Spike** » Thu Jun 02, 2011 8:42 am

Thanks, Airmun.

That is exactly the path I'm taking.

Spike

bbap · Post by **bbap** » Thu Jun 02, 2011 12:30 pm

You must have a well charged battery. Stick it on the charger for 3 hours and re-try.

If it previously started, and:
Compression (you have that), and
A good spark on both sides, and
Fuel, AND
you have not messed with the timing, it should start.

In my opinion, these are the issues about 95% of the time. Always assume the simple and don't go looking for the complex until the simple issues are eliminated twice!

Spike · Post by **Spike** » Thu Jun 02, 2011 12:58 pm

bbap,

Good ideas. Now, assuming compression is good, I'll be looking at spark next, maybe today.

The battery was new when the bike ran a few months ago. It was allowed to run down. Since then, it was on a charger for three -four hours, and has been on a Battery Tender for several days. It should be good and it will be kept charged now.

Timing was set by me to make the bike run a few months ago. Then changed by another in an attempt to get it running again. The points are new correct oem Honda points. I'll be looking for spark first then check timing again.

It is easy to comfirm spark presence, Any recommendations as to how to identify sufficient spark?

Spike

bbap · Post by **bbap** » Thu Jun 02, 2011 1:20 pm

There are a number of posts on this site for checking of adequacy of spark including checking the magnets on the flywheel, but to check to see if there is a spark, simply ground the plug after connecting, turn key on and turn over and watch for spark jumping the gap to ground.

I use this: http://www.harborfreight.com/90-inline- ... -4445.html
as it allows for better placement of plugs and easier viewing....

Look for the EZ things first. It's almost always there. Since the timeing has been changed, that may be your issue....Steve